|Publication number||US8071428 B2|
|Application number||US 12/388,140|
|Publication date||Dec 6, 2011|
|Filing date||Feb 18, 2009|
|Priority date||Jul 2, 2007|
|Also published as||CN101339927A, DE102008028072A1, US8829663, US20090008793, US20090155956|
|Publication number||12388140, 388140, US 8071428 B2, US 8071428B2, US-B2-8071428, US8071428 B2, US8071428B2|
|Inventors||Jens Pohl, Markus Brunnbauer, Irmgard Escher-Poeppel, Thorsten Meyer|
|Original Assignee||Infineon Technologies Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (34), Non-Patent Citations (2), Referenced by (2), Classifications (54), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This Utility patent application is a continuation of U.S. application Ser. No. 11/772,539, filed Jul. 2, 2007, which is incorporated herein by reference in its entirety.
This disclosure relates to semiconductor devices and methods to manufacture semiconductor devices.
For high system integration it is useful to stack integrated circuits, sensors, micromechanical apparatuses or other devices on top of each other. In order to be able to electrically connect the stacked devices, it may be useful for at least some of the stacked devices to be provided with electrical conductive feedthroughs from their top surface to their bottom surface.
For these and other reasons there is a need for the present invention.
The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles of the invention. Other embodiments of the present invention and many of the intended advantages of the present invention will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
In the following disclosure, embodiments of the invention are described with reference to the drawings, wherein like reference numerals are generally utilized to refer to like elements throughout, and wherein the various structures are not necessarily drawn to scale. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects of embodiments of the invention. It may be evident, however, to one skilled in the art that one or more aspects of the embodiments of the invention may be practiced with a lesser degree of these specific details. In other instances, known structures and devices are illustrated in block diagram form in order to facilitate describing one or more aspects of the embodiments of the invention. The following description is therefore not to be taken in a limiting sense, and the scope of the invention is defined by the appended claims.
Devices with a semiconductor chip embedded in a molding compound are described below. The semiconductor chips may be of extremely different types and may include for example integrated electrical or electro-optical circuits. The semiconductor chips may be configured as MEMS (micro-electro mechanical systems) and may include micro-mechanical structures, such as bridges, membranes or tongue structures. The semiconductor chips may be configured as sensors or actuators, for example pressure sensors, acceleration sensors, rotation sensors, microphones etc. Semiconductor chips in which such functional elements are embedded generally contain electronic circuits which serve for driving the functional elements or further process signals generated by the functional elements. The semiconductor chips need not be manufactured from specific semiconductor material and, furthermore, may contain inorganic and/or organic materials that are not semiconductors, such as for example insulators, plastics or metals.
The semiconductor chips may have contact pads which allow electrical contact to be made with the semiconductor chip. The contact pads may be composed of any desired electrical conductive material, for example of a metal, such as aluminum, gold or copper, a metal alloy or an electrical conductive organic material. The contact pads may be situated on the active surfaces of the semiconductor chips or on other surfaces of the semiconductor chips.
The devices described in the following include a molding compound layer covering at least parts of the semiconductor chips. The molding compound layer may be any appropriate thermoplastic or thermosetting material. Various techniques may be employed to cover the semiconductor chips with the molding compound layer, for example compression molding or injection molding. The molding compound may, for example, surround a main surface and side surfaces of the semiconductor chip. The molding compound layer may extend beyond the semiconductor chip so that the dimensions of a main surface of the molding compound layer may be larger than the dimensions of a main surface of the semiconductor chip.
A first electrically conductive layer may be applied to the molding compound layer. The first electrically conductive layer may be used to electrically couple contact pads of the semiconductor chips to external contacts. The first electrically conductive layer may be a redistribution layer or may be a part of it. The first electrically conductive layer may be manufactured with any desired geometric shape and any desired material composition. The first electrically conductive layer may, for example, be composed of linear conductor tracks, or may have special shapes, for example to form inductor coils, but may also be in the form of a layer covering an area. Any desired electrically conductive material, such as metals, for example aluminum, gold or copper, metal alloys or organic conductors, may be used as the material. The first electrically conductive layer need not be homogeneous or manufactured from just one material, that is to say various compositions and concentrations of the materials contained in the first electrically conductive layer are possible. The first electrically conductive layer may be arranged above or below or between dielectric layers. Furthermore, it can be provided that several first electrically conductive layers are stacked on top of each other, for example, in order to obtain conductor tracks crossing each other.
Through holes may be arranged in the molding compound layer, which may extend from one main surface of the molding compound layer to its other main surface or from one main surface of the device to its other main surface. The through holes may be generated by mechanical drilling, laser beam drilling, etching methods, stamping methods or any other appropriate method. The aspect ratio of the through holes, which is the ratio of their widths to their lengths, may be in the range from 1:1 to 1:5 and in particular from 1:2 to 1:4. The widths of the through holes may be in the range between 50 to 500 μm and in particular in the range between 100 and 200 μm. The lengths of the through holes may be in the range between 100 and 1000 μm and in particular in the range between 500 and 800 μm.
The molding compound layer may contain a filling material consisting of small particles of glass (SiO2), or other electrically insulating mineral filler materials like Al2O3, or organic filler materials. The used grain size of the filling material may depend on the width of the through holes to be generated in the molding compound layer. For through holes with widths in the range of 100 μm or smaller a grain size of 10 μm or less may be used. For through holes with widths above 100 μm an average grain size of about 20 to 30 μm may be used.
The through holes may be lined with a second electrically conductive layer. For this layer, electrically conductive materials, such as metals, for example aluminum, gold or copper, metal alloys or organic conductors, may be used as the material. The second conductive layer may also consist of different single layers, for example a titanium or palladium based seed layer, a copper layer and a surface finish of nickel and gold. Other layer variations are possible. The second electrically conductive layer may have a thickness in the range between 0.2 and 75 μm and in particular in the range between 1 and 10 μm. The second electrically conductive layer deposited on the surfaces of the through holes forms a vertical contact that connects one main surface of the molding compound layer with its other main surface. After the generation of the second electrically conductive layer the through holes may be filled with a solder material or another electrically conductive material. The solder material may be made of metal alloys which are composed, for example, from the following materials: SnPb, SnAg, SnAgCu, SnAgCuNi, SnAu, SnCu and/or SnBi. The solder material may be lead-free. Alternatively, the through holes may not be coated with the second electrically conductive layer, but are filled with the solder material. According to yet another alternative, the through holes may be coated with the second electrically conductive layer, but are left unfilled or may be filled or coated with an electrically insulating material. For corrosion protection, the second electrically conductive layer may be coated with a corrosion resistant metal layer, such as a NiAu surface. Filling or coating the through holes with an appropriate material may help to protect the second electrically conductive layer against corrosion.
A third electrically conductive layer may be applied to the surface of the molding compound layer opposite the surface to which the first electrically conductive layer is applied. The third electrically conductive layer may be manufactured with any desired geometric shape and any desired material composition. The third electrically conductive layer may, for example, be composed of linear conductor tracks, or special shapes e.g., to form inductor coils, but may also be in the form of a layer covering an area. Any desired electrically conductive material, such as metals, for example aluminum, gold or copper, metal alloys or organic conductors, may be used as the material. The third electrically conductive layer may be in contact with the second electrically conductive layer and/or the solder material arranged in the through holes. The third electrically conductive layer may facilitate to contact the semiconductor chip from the top side of the device.
The first electrically conductive layer 107 together with the dielectric layers 109 and 112 form a redistribution layer. The dielectric layer 109 prevents short circuits of the conductor tracks 107 with the active main surface of the first semiconductor chip 101. The first electrically conductive layer 107 couples the contact pads 108 of the first semiconductor chip 101 to the external contact pads 113. The external contact pads 113 allow to contact the first semiconductor chip 101 from outside the device 100-3. The dielectric layer 112 protects the conductor tracks 107 and may be implemented as a solder stop layer in case solder deposits, for example solder balls, are placed on the external contact pads 113. It is to be noted that the number of layers of the redistribution layer is not limited to three. To facilitate a design where the conductor tracks 107 cross each other, further metallization layers and dielectric layers may be provided. Also, there may be a further dielectric layer arranged between the third electrically conductive layer 111 and the molding compound layer 102. Furthermore, the third electrically conductive layer 111 may also be protected by a dielectric layer 114. The dielectric layer 114 may also have openings to form external contact pads 115 on the top of the device 100-3. The external contact pads 115 may be electrically coupled to the contact pads 108 of the first semiconductor chip 101 via the second electrically conductive layer 110 coating the surface of the through holes 103 and/or the material 106, for example solder, deposited in the through holes 103. The dielectric layers 109, 112 and 114 may be manufactured from any electrically insulating material, for example, silicon nitride or photoresist.
It may be provided that the external contact pads 113 are not directly situated below the through holes 103, but may rather be shifted away from the through holes 103. This may prevent the solder material 106 deposited in the through holes 103 to leak from the through holes 103 when the solder deposited on the external contact pads 113 is melted.
The molding compound layer 102 allows the redistribution layers to extend beyond the first semiconductor chip 101. The external contact pads 113 and/or 115 therefore do not need to be arranged in the area of the first semiconductor chip 101 but can be distributed over a larger area. The increased area which is available for arrangement of the external contact pads 113 and 115 as a result of the molding compound layer 102 means that the external contact pads 113 and 115 cannot only be placed at a great distance from one another, but that the maximum number of external contact pads 113 and 115 which can be placed there is likewise increased compared to the situation when all the external contact pads 113 and 115 are placed within the area of the main surfaces of the first semiconductor chip 101. The distance between neighboring contact pads 113 and/or 115 may be in the range between 100 and 600 μm and in particular in the range between 300 and 500 μm.
The semiconductor chips 101 and 118 may have been manufactured on the same wafer, but may alternatively have been manufactured on different wafers. Furthermore, the semiconductor chips 101 and 118 may be physically identical, but may also contain different integrated circuits. The active main surfaces of the semiconductor chips 101 and 118 may face the carrier 119 when attached to the carrier 119.
After the semiconductor chips 101 and 118 were mounted on the carrier 119, they are encapsulated by molding using a thermoplastic or thermosetting molding compound 102 (see
The semiconductor chips 101 and 118 covered with the molding compound 102 are released from the carrier 119, and the adhesive tape is pealed from the semiconductor chips 101 and 118 as well as from the molding compound layer 102. The adhesive tape may feature thermo-release properties, which allow the removal of the adhesive tape during a heat-treatment. The removal of the adhesive tape from the carrier 119 is carried out at an appropriate temperature, which depends on the thermo-release properties of the adhesive tape and is usually higher than 150° C., in particular approximately 200° C. After removing the carrier 119, the semiconductor chips 101 and 118 are held together by the molding compound layer 102.
As illustrated in
One or more cleaning steps may follow the formation of the through holes 103. For example, the molding compound layer 102 together with the semiconductor chips 101 and 118 may be dipped into an ultrasonic bath containing water and/or isopropanol.
Prior to the generation of the second electrically conductive layer 110, a masking layer 120 may be deposited onto the active main surfaces of the semiconductor chips 101 and 118 (see
Thereafter the surface of the reconfigured wafer may be completely metallized with a metal layer 121 as illustrated in
The metal layer 121 may be structured in order to generate the desired metallic structures using lithographic and etching steps. As a result the second electrically conductive layers 110 are obtained coating the surfaces of the through holes 103 (see
It may be provided that an electrically insulating material, such as epoxy, is filled into the through holes 103 coated with the second electrically conductive layer 110. It may alternatively be provided that the coated through holes 103 are coated with a further layer, such as a nickel gold layer, and that the remaining parts of the through holes 103 are left unfilled. Both, the electrically insulating material as well as the further layer, may protect the second electrically conductive layer 110 against corrosion.
According to a further embodiment, the though holes 103 are filled with a solder material 106. For that, a flux material
123 together with the solder material 106 may be placed on the land pads 122 (see
The flux material 123 may be printed on the land pads 122. A stencil may be placed over the molding compound layer 102 and the flux material 123 may be pressed through the stencil with a squeegee. The solder material 106 may be printed onto the flux material 123. Alternatively, a pick and place process or a shacking process may be used to place the solder material 106 in the form of solder balls on the land pads 122. The solder material 106 may be a lead-free metal alloy, such as SnPb, SnAg, SnAgCu, SnAgCuNi, SnAu, SnCu or SnBi. The flux material 123 may, for example, be a no-clean flux, which evaporates during the soldering process.
The flux material 123 and the solder material 106 are heated up above the melting temperature of the solder material 106, for example to temperatures in the range between 160° C. and 300° C. and in particular in the range between 180° C. and 260° C. The melted solder material 106 then flows into the through holes 103 and solidifies there (see
The redistribution layers including the electrically conductive layers 107 and 115 as well as the dielectric layers 109, 112 and 114 may be generated using standard techniques (see
The dielectric layers 112 and 114 are opened at the positions of the external contact pads 113 and 115. Solder balls 124 may be placed on the external contacts pads 113 and/or 115 (see
After the generation of the electrically conductive layers 107, 110 and 111, further dielectric layers 112 and 125 may be deposited (see
In addition, while a particular feature or aspect of an embodiment of the invention may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and for any given or particular application. Furthermore, to the extent that the terms “include”, “have”, “with”, or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprise”. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements co-operate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other. Furthermore, it should be understood that embodiments of the invention may be implemented in discrete circuits, partially integrated circuits or fully integrated circuits or programming means. Also, the term “exemplary” is merely meant as an example, rather than the best or optimal. It is also to be appreciated that features and/or elements depicted herein are illustrated with particular dimensions relative to one another for purposes of simplicity and ease of understanding, and that actual dimensions may differ substantially from that illustrated herein.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments illustrated and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
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|U.S. Classification||438/112, 438/68, 438/118, 438/110, 438/127, 438/111, 438/113|
|Cooperative Classification||H01L2924/181, H01L24/19, H01L2224/0401, H01L2924/1461, H01L2924/01005, H01L2924/01046, H01L2224/82047, H01L23/3107, H01L2924/01068, H01L2224/18, H01L25/105, H01L2924/15331, H01L2924/01078, H01L21/568, H01L2924/01027, H01L2924/15311, H01L2924/01033, H01L21/6835, H01L24/96, H01L2924/01006, H01L2924/01013, H01L23/5389, H01L2924/01082, H01L24/82, H01L2924/30107, H01L2924/19042, H01L2224/82039, H01L2924/12044, H01L2924/01015, H01L2224/97, H01L2924/14, H01L24/97, H01L2924/01079, H01L2924/01029, H01L2225/1035, H01L2225/1058, H01L2224/12105, H01L2224/04105|
|European Classification||H01L24/18, H01L21/683T, H01L23/31H, H01L25/10J, H01L24/82, H01L24/96, H01L24/97, H01L21/56T|
|Aug 2, 2011||AS||Assignment|
Owner name: INFINEON TECHNOLOGIES AG, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:POHL, JENS;BRUNNBAUER, MARKUS;ESCHER-POEPPEL, IRMGARD;AND OTHERS;SIGNING DATES FROM 20070822 TO 20070827;REEL/FRAME:026687/0992
|May 28, 2015||FPAY||Fee payment|
Year of fee payment: 4